The specific objective of this project is to study the biology of Gamboa virus (family Bunyaviridae) in its presumed mosquito vector, Aedeomyia squamipennis, under natural conditions. The ultimate goal of the research is to better understand how arthropod-borne viruses are maintained in nature. Multiple recoveries of Gamboa virus from field-collected A. squamipennis larvae suggest that the virus is transovarially transmitted in this mosquito species. In the proposed project, we will attempt to determine the mechanism by which Gamboa virus is vertically transmitted in A. squamipennis and if the virus can be maintained in mosquitoes by transmission alone. In this project, Gamboa virus is being studied as a model for the behavior and survival strategy of other more important arthropod-borne viruses. The hypothesis to be tested is that Gamboa virus is maintained in A. squamipennis population in nature by cytoplasmic (estrachromosomal) inheritance, in a manner similar to that described for sigma virus (family Rhabdoviridae) in Drosophila melanogaster. The project consists of 7 parts and includes both field and laboratory studies, all of which will be carried out in Panama at the facilities of the Gorgas Memorial Laboratory. The results of this research should provide new information about the maintenance mechanism of a number of arthropod-borne viruses of public health and veterinary importance. Proof of the proposed hypothesis would alter current concepts about the epidemiology and control of a number of arthropod-borne viral diseases.